1. Field of the Invention
The present invention relates to a temperature adaptive circuit, a circuit temperature raising method and a circuit temperature raising program capable of operating a circuit such as an LSI circuit, etc., in a temperature range in which the circuit operates normally even at the time when power is turned on or the like.
2. Description of the Related Art
In recent years, in high performance LSI (Large Scale Integrated) circuits, power consumption is increasing in accordance with higher clock frequencies and increased transistor current, so the temperature of an LSI chip during its operation becomes generally about 30–70 degrees in centigrade. In addition, changes in transistor characteristics and in wiring resistances take place in accordance with a change in the temperature of the chip, so operation timing inside the chip is caused to change. Thus, it is necessary to design the chip in such a manner that the chip can operate normally in the entire temperature range estimated.
Here, note that for example, a first patent document (Japanese patent application laid-open No. H6-201780 (pages 3–4 and FIG. 1)) is cited as a prior art document relevant to the present invention. An integrated circuit disclosed in the first patent document has a function of making its testing easy or simple.
However, considering when the chip is in operation, a temperature rise more than a certain degree of the chip is expected due to the operation thereof, whereas considering when the chip starts to operate, the chip temperature is low due to the low temperature of ambient air. Thus, it is necessary for the chip to operate normally in both of these cases. Here, a problem arises in that when a delay is increased so as to permit the chip to operate normally at its low temperatures, i.e., in a state where the chip can operate at high speed, an upper limit for the operation speed of the chip is suppressed and at the same time the man-hour of a countermeasure against racing is increased, too.